1. Field of the Invention
This invention relates to a dye-forming electrically activatable recording element and process. One aspect of the invention relates to the use of a certain polyvinyl ester in the electrically active conductive layer, referred to herein as a polymeric EAC layer, in an electrically activatable recording element which is capable of producing a dye image and silver image by dry development processes.
2. Description of the State of the Art
Production of a dye image and silver image in an electrically activatable recording material by dry development techniques is described in Research Disclosure, October, 1979, Item No. 18627. In accord with that description, production of a dye image and silver image is accomplished by means of an electrically activatable recording element comprising an electrically conductive support, such as a poly(ethylene terephthalate) film with a cermet coating, having thereon, in sequence:
(a) an electrically activated recording layer comprising an organic silver salt and a reducing agent, PA0 (b) a photoconductive layer separated from (a) by an air gap of up to 20 microns, and PA0 (c) an electrically conductive layer on (b), wherein the recording layer comprises, in reactive association, PA0 (a) a polymeric electrically active conductive layer, PA0 (b) an electrically activatable recording layer comprising: PA0 (c) a photoconductive layer separated from (b) by an air gap of up to 20 microns or separated from (b) by an electrically conductive interlayer, and PA0 (d) an electrically conductive layer, preferably on a second support.
(A) a dye-forming coupler, and PA1 (B) an oxidation-reduction combination comprising: PA1 R.sup.1 and R.sup.3 are individually hydrogen or methyl; PA1 R.sup.2 is alkyl containing 2 to 20 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, decyl and eicosyl; PA1 x is 0 or 1; PA1 y is 0 to 4; PA1 R.sup.4 is C.sub.6 H.sub.5-z X.sub.z ; wherein z is 1 to 5; PA1 X is chlorine, bromine or iodine; PA1 n is 40 to 100 weight percent; and PA1 wherein the copolymer has a glass transition temperature which is within the range of 20.degree. C. to 40.degree. C., preferably 20.degree. C. to 30.degree. C. PA1 (A) a dye-forming coupler, and PA1 (B) an oxidation-reduction combination comprising: PA1 (I) imagewise applying an electric potential, of a magnitude and for a time sufficient to produce in the image areas a charge density which enables formation of a latent image, such as a charge density within the range of about 10.sup.-8 to about 10.sup.-5 coulomb/cm.sup.2 in an electrically activatable recording layer of a charge sensitive recording element having a polymeric electrically active conductive layer according to the invention; and, then PA1 (II) heating the element substantially uniformly at a temperature and for a time sufficient to produce a dye image and silver image in the recording layer.
(i) an organic silver salt oxidizing agent, with PA2 (ii) a reducing agent which, in its oxidized form, forms a dye with the dye-forming coupler. PA2 (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriazole derivative with PA2 (ii) a reducing agent which, in its oxidized form, forms a dye with the dye-forming coupler,
Such an electrically activated recording element enables formation of a dye image and silver image by heat processing after imagewise exposure. It has been desirable to increase the charge sensitivity of such elements. Increased charge sensitivity would lower the levels of charge required to form a latent image in the electrically activated recording layer.
Attempts have been made to increase charge sensitivity by means of various polymeric layers between the electrically conductive support and the electrically activated recording layer. However, many polymeric materials do not provide a suitable increase in charge sensitivity. This is illustrated by the comparative information in U.S. Pat. No. 4,309,497. While certain halogen-containing polyesters in electrically active conductive layers have provided increased charge sensitivity in an electrically activatable recording element, it has been found that halogen-containing polyesters as a class do not provide such increased charge sensitivity. For example, it was found, as illustrated in following comparative examples 16, 17, 18, 19 and 20, that poly(pentachlorophenoxyethyl methacrylate), poly(pentachlorophenoxyethylacrylate-co-N-laurylmethacrylate), poly(pentachlorophenoxyethylmethacrylate-co-N-laurylmethacrylate), poly(tribromophenoxyhexyl acrylate), and poly(tribromophenoxybutyl acrylate) do not provide such increased charge sensitivity. It has been desirable to replace the halogen-containing polyesters described in U.S. Pat. No. 4,309,497 with halogen-containing polyvinyl esters because the halogen-containing polyvinyl esters are simpler to prepare. A problem was what halogen-containing polyvinyl esters were useful to provide increased charge sensitivity in an electrically active conductive layer. No answer to this problem was suggested in the art. No suggestion was made in the art that a particular glass transition temperature was an important factor in the answer to the problem.